The invention relates to a conveyor for elongate components designed with a head and a shank, in particular rivets, screws, weld studs and the like, according to the preamble of claim 1.
It is known to use conveyors for the automated supply of elongate components designed with a head and a shank. These conveyors are used, in-particular, for stud welding devices, punch riveting devices or the like.
German Patent No. 2 403 904 discloses a conveyor for elongate components designed with a head and a shank. The conveyor comprises a feed duct which passes into a conveying duct. Inside the conveying duct is arranged a plunger by means of which the component can be conveyed within the conveying duct to a free end portion of the conveying duct. The plunger can be pulled back sufficiently far within the conveying duct that it clears the feed duct. According to German Patent No. 2 403 904, the conveying duct extends such that the components pass into the conveying duct while utilizing the force of gravity. The components are introduced into the feed duct separately. Owing to the design of the conveyor according to German Patent No. 2 403 904, the cycle time of the conveyor is determined substantially by the feed rate of the components within the feed duct.
To improve the cycle times it is known to increase the feed rate of the components.
If the feed rate is increased, however, there is a risk that the components to be fed will jam or tilt within the feed duct.
To solve this problem, for example, U.S. Pat. No. 5,588,576 proposes a feed arrangement comprising a gripping tongs with at least two gripping arms provided with a front gripping region and a rear pivot axis region. The gripping arms are spring loaded and have a portion through which the feed duct to the gripping region of the gripping arms taper. Owing to this design of the feed arrangement, the components which are fed individually at high speed, preferably pneumatically, are initially decelerated and then come to a standstill in the gripping region.
A problem with this feed arrangement which operates quite satisfactorily is that when components with identical geometry but of different materials are exchanged, the deceleration effect of the gripping tongs is too great, so the components do not pass to the transfer region. With components having a very great mass (great weight), it can happen that the deceleration effect is too slight so the component jumps out of the transfer region.
During the feeding of components in a feed conduit, the speed of the component is reduced owing to frictional losses between the component and the feed duct. In particular with relatively long feed conduits, it may happen that the component does not reach the transfer region. It may also happen that the kinetic energy of the component is too low to spread the gripping tongs. To prevent this, the components are conveyed into the feed duct at high speed.